1968—What does Chief Justice Earl Warren do when he encounters a 45-year-old precedent that has stood (in his own words) as an “impenetrable barrier” to suits by federal taxpayers (in their capacity as taxpayers) challenging the constitutionality of the uses for which Congress has authorized the expenditure of public funds? In Flast v. Cohen, Warren’s majority opinion for eight justices concocts an unprincipled, ad hoc exception for taxpayer suits challenging federal spending on Establishment Clause grounds.